Working Principle of Fuel Cell

Fuel cell

• In this theory, working principle, parts of fuel cell, fuel cell voltage and fuel cell efficiency is given. 
• The fuel cells are electrochemical devices that convert the chemical energy of gaseous fuel directly into electricity.
• The fuel cell principle was discovered by William R Grove, a British Physicist in 1839. A fuel cell consists of an electrolyte (either solid or liquid) sandwiched between two electrodes. 
• The hydrogen gas passes over anode electrode with the help of a catalyst separate into electrons and hydrogen protons.

        2H₂ → 4H⁺+ 4e^-

• The protons flow to other electrode called cathode through electrolyte whereas the electrons flow through an external circuit therefore creating electricity. 
• The hydrogen protons and electrons combine with oxygen flow through cathode and produce water as only waste due to chemical reaction.

       O₂ + 4H⁺ + 4e^- → 2H₂O

• Overall chemical reaction

       2H₂ + O₂ → 2H₂O

Parts Of Fuel Cells

Membrane electrodes assemble (MEA)

• It is a compact unit producing output power of the fuel cells. 
• Its thickness is in terms of few hundred microns. 
• It consists of two electrodes with their catalyst and electrolyte.

Electrolyte

• The electrolytes are thin plastic like / solid polymer / liquid membranes.
• Their main function is to pass the hydrogen positive ions from the anode to cathode while completely block the free electrons from moving in this direction. 
• If the free electrons could pass through electrolyte, chemical reaction will be hold up.

Electrodes

• Every fuel cell consists of two electrodes that are anode and cathode. A catalyst is required for each electrode.

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Fuel Cell Catalyst

• It is special chemical material used to increase the rate of reactions without being consumed. 
• Most types of fuel cells used platinum (Pt) and its group as catalyst at the two electrodes. 
• The Pt catalyst at the anode helps in splitting the hydrogen molecules into free electrons and positive protons. 
• At the cathode, it enables oxygen reduction. 
• A catalyst of a fuel cell is one which has high electric conductivity, stable contact the electrolyte and reactance gases.

Fuel Cell Voltage

• The voltage produced from one cell lies between 0 to 1 voltage and depending upon operating condition, type of electrolyte and size of load connected to the fuel cell. 
• The typical value of fuel cell is about 0.7 V. 
• In order to higher voltage, multiple cells are connected in series. The total stack voltage

                  = Average cell voltage × Number of cells

• There is electrical resistance in the fuel cell, resulting heat loss occurs in it. The heat is released from the fuel cell reaction.

Fuel Cell Efficiency

• The fuel cell efficiency is greatly affected by quality of electrolyte. 
• It increases with increasing the membrane ability to block electrons generated form the oxidation of the anode from reaching the cathode.
• The electrolyte must be chosen carefully such that allows only position ions to pass through is in one direction only towards cathode. 
• A catalyst is added in order to reduce the reaction energy on the two electrodes.